The Rotating Frame feature exerts fictitious forces on particles that are moving in a rotating frame of reference. Optionally, it also applies an offset to the initial velocity of released particles, depending on whether their velocity is initialized with respect to the inertial (nonaccelerating) frame or the rotating (noninertial) frame.

Consider a particle of mass mp (SI unit: kg) moving in a noninertial frame of reference with translational acceleration W (SI unit: m/s2) that is rotating at angular velocity Ω (SI unit: rad/s) about a center of rotation with position rbp (SI unit: m). Note that Ω is a vector quantity that also indicates the orientation of the axis of rotation and the sense of rotation (clockwise or counterclockwise). The total fictitious force Ffr (SI unit: N) exerted on a particle in this noninertial frame of reference is (Ref. 1)

The displacement r (SI unit: m) of the particle is defined with respect to the center of rotation,

where q (SI unit: m) is the particle position. The Rotating Frame feature only accounts for rotational motion of the frame, not translational motion, so the term Facc is canceled.

When the Rotating Frame feature is active, it is possible to subtract the frame velocity from the initial particle velocity when releasing particles. This is equivalent to specifying the initial particle velocity with respect to the inertial frame. The relationship between the initial velocity in the inertial frame vi,in and in the rotating frame vi,rot is

where vf is the frame velocity at the particle’s position,